Automatic oven-temperature control



Feb. 1l, 1930. J. P. scHoENBERGER AUTOMATIC OVEN TEMPERATURE CONTROLFiled Jan. l5. 192'? m INVENTOR.

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Patented Feb. 11, 193@ STATES PATENT cries JOHN P. SCHOENBEBGER, F SANJOSE, CALIFORNA, ASSIGNOR OF TVJO-THIRDS T0 DANIEL RYGEL, OF OAKLAEIE,CALIFORNIA., AND E. J. BURT, OF SAN JOSE, CALT- FORNIA.

AUTOMATIC OVEN-TEMPERATURE CONTROL Application led January 15, 1927.Serial No. 161,333.

This invention relates to improvements in control devices tor theelements oit' electric cooking ovens to control the heat ot the oven,and particularly represents an improvement over the torm ot controldevice shown in m cri-pending application tor patent, filed July 31st,1926, Serial No. 126,125.

The principal object ot the present invention is to provide a controlapparatus for the l0 same purpose as the former but ot simplied and morecompact torni. such as is less liable to become deranged in action,which is easy to apply to the oven and which may be readily removed as asingle unit whenever necessary. A further object ot the invention is toprovide the control apparatus with a plurality of switch or Contactpoints arranged in cooperating pairs which may be connected to oney ormore oven heating elements and the opening and closing ot whose circuitswhile taking place simultaneously will loe independent of each other.

A further object ot the invention is to produce a simple and inexpensivedevice and yet one which will be exceedingly effective for the purposetor which it is designed.

These objects l accomplish by means ot such structure and relativearrangement of parts as will fully appear by a. perusal of the followingspecification and claims.

ln the drawings similar characters of reference indicate correspondingparts in the several views:

Fig. 1 is a sectional elevation ot my improved torm ot' controlapparatus.

Fig. 2 is an outer end view ot the same with the cover and operatinghandle removed.

Fig. 3 is an inner end view of the housing member with the cap removed.

Referring now more particularly to the characters ot reference on thedrawings, the numeral 1 denotes the outer side wall ot an oven orconventional form having an electric heating device mounted therein andpreferably depending from the inner top wall 2 ot the oven, each heatingldevice including a heating element 3 of suitable character.

My improved apparatus to control the opening and closing of the elementcircuit by the heat generated in the oven by said element comprises amain centrally oriiiced supporting plate 4t rigidly secured on theoutside of the wall 1. Projecting inwardly oi' the oven from the plateis a tubular housing- 5 of expansible metal in which adjacent its innerend is rigidly mounted a longitudinally slotted block G having atransverse pin 7 therethrough. Pivoted at one end on the pin is a lever8 ot a metal having the same coefficientot expansion as the housing. Thelever eX- tends to a point adjacent the plate et and at said end issecured an extension 9 which projects through and beyond the plate andsupports a cross bar 10 ot insulation material on its outer end.Projecting loosely7 through the bar 10 on each side ot the support 9 tortree vertical movement are pins 11. rlhe lower ends ot these pins carrycontact pads 12 arranged to normally engage similar pads 13 mounted onbrackets 14. rllhe brackets are secured to the outer tace of a centrallyoriticed disc 15 of porcelain or the like, which disc is removablysecured to the plate 4 by suitable means such as screws 16. @n the upperends ot the pins 11 are mounted binding nuts 17 which are clear of thecross bar 10 a Certain distance when the contact pads are engaged.

Disposed in the housing 5 and extending lengthwise under and normallyparallel t0 the lever 8 is a bar 18 ot non-expansible metal. This bar atits inner end rests on the block 6 or on the bottom ot the housing andhas at such end an upstanding lug 19 adapted to engage a shoulder 2Oiormed on the lever 8 and disposed sulistantially radial to and belowthe pivotal pin head ot the lug, or toward the free end oiE the leverwith respect to said lug. The bar at its opposite end projects throughthe plate 4 and member 15 and is threaded at such end to engage a tappedsleeve 21 on the outer end of which is mounted a. calibrated handle 22.The sleeve at its inner end bears against a plate 28 mounted inside andagainst the plate 4, to which the housing 5 and said plate 23 areattached. The sleeve is held in constant engagement with said plate 23by a spring 24 engaging the opposite. end ot the sleeve and alsopressing against a cover member 25 which is removably but rigidlysecured to the plate 4 and which encloses the contact structure andadjacent parts. The handle and sleeve therefore cannot movelongitudinally and the rotation of the handle will cause the bar 18 tobe moved lengthwise in the housing, so that the distance between the lug19 and shoulder 20 may be altered. The extension member 9 also projectsthrough the plate 23 above the bar 18 and when the lever 8 is in itsnormal or cold condition, rests on said plate 23 so that the downwardmovement of the extension and lever is limited. The bar 18 cannot rotatesince it is rectangular where it enters the block 6 and the slot in thelatter is shaped to correspond. lt will therefore be seen that as thehousing 5 and lever 8 expand with heatthe shoulder 2O approaches thenon-moving lug 19. When these parts engage each other, further eX-pansion of the housing causes the vlever to be raised about its pivotand as soon as the slack between the nuts 17 and the bar 10 is taken upthe contacts will be broken, as will be evident. rlhe length of thelever is such that a'very slight movement of the shoulder is suiiicientto impart considerable movement to the opposite end of the lever, sothat the breaking of the contacts takes place without any undue lag.

lt will be evident that the amount of ei;- pansion of the housing andlever (which is governed by the temperature in the oven generated by theelement 3) before the engagement of the lug and shoulder and theconsequent breaking of the contacts takes place,is determined by theinitial setting of the lug relative to the shoulder. lt is therefore aneasy matter to calibrate the handle so that the rotation of the same acertain amount relative to a fixed mark on the adj acent face of thecover 25, will accurately determine at what temperature the contactswill break. lt may be possible that the housing 5 after a certain periodof use will become permanently lengthened or distorted so that therotation of the handle to a predetermined position no longer causes thebreaking of the contacts at a corresponding heat. rlortake care of suchcontingency l mount the handle 22 on a core 26 which is rigidlyV screwedonto the sleeve 2l, and normally Ahold the core and handle immovablerelative to each other by a set screw 27. Upon loosen,- ing the setscrew the handle may be rotated on the core independently of the sleeve,so that no movement will be imparted to the bar 18, and the calibrationof tie handle relative to the 'fixed mark on the cover may be then resetas may be necessary. When the handle has been moved to a proper positionthe set screw is again tightened up.

lf it is desired to remove the device from the oven as a unit, thescrews el which secure plate 4 to the oven, and which are accessiblewithout removing the cover 25, are withdrawn. If it is desired to removethe cover, the handle and core are unscrewed from the sleeve, whichpermits the wiring as shownto be disconnected and the interior partsinspected. The entire structure may then be withdrawn from. the oven,and the various parts may then be dissembled from each other.

Each of the oven elements may be wired to one of the brackets and thecorresponding contact pin in any suitable manner so that the circuit tothe element will be broken when the adjacent contacts 12 and 13 areseparated. It will be seen that by the use of separated pairs of thesecontact units two or more heating elements may be connected to a sourceof current with each element circuit independentof each other, and yetin such manner that all circuits will be broken simultaneously.

The device is therefore suitable to be used,

whether the oven-is of the single or double element type. i Y

rlhe purpose of the increasing height of the housing toward itsk outerend is to enable the operator to adjust the bar 18 when the circuit hasbeen broken with a high heat, and it is desired to make adjustments tocause the contacts to be broken at a lower heat, while the housing isstill in a hot and expanded condition. To make such adjustment it willbe evi-f dent thatthe lug 19 on the bar 18 will be pulled closer towardthe outer end of the de-v vice, and when such movementn of the lug takesplace when the shoulder 20 is already engaged therewith, it is necessaryof course i that sufficient vertical space Vbe had in the outer end ofthe casing to allow the lever to swing upwardly as the lug is thusadjusted.

As far as the operation of the device is concerned, the lever 8 could bemade non-eXpansible. By making it expansible however and with the samecoefficient of expansion as the lever, the contact points are alwayskept in direct vertical alinement.

W'hile l have shown and described this device as being particularlyintended for use in an oven, it is also adapted for the control of thetemperatures of rooms, furnaces, fluids, etc. when electricity is usedto heat or control heat, orto operate motors in connection with heatingdevices.

From the foregoing description it will be readily' seen that I haveproduced such a device as substantially fulfills the objects of theinvention as set forth herein.

While this specification sets forth in detail the present and preferredconstruction of theV device, still in practice such deviations from suchdetail may be resorted to as do not form a departure from the spirit ofthe invention,

as defined by the appended claims.

Having thus described my invention'what I claim as new and useful anddesire to secure by Letters Patent is:

1. A thermostatically controlled switch structure including a horizontallever adapted to be projected into a zone oi heat, an expansible housingsurrounding the lever, a transverse pivot for the inner end of the leversecured in the housing, a structure adapted to be mounted in a iixedposition to which the housing is secured at its end opposite to thepivot, a contact mounted on the free end of the lever, a contact iixedon said structure under the lever contact and normally engaged thereby,a non-expansible bar extending from said structure along and under thelever to the pivoted end thereof,4

,said lever having a substantially radial shoulder below its pivot, anda lug upstanding from the bar beyond the shoulder to be engaged therebyafter the housing has expanded a certain distance.

2. A thermostat switch comprising` a longitudinally expansible member tobe projected into a zone of heat, a support for the outer end of saidmember, a lever extending lengthwise of said member from the support andpivoted onto the member adjacent the inner end of the latter,cooperating contacts mounted on the support and the outer end of thelever, means cooperating with the lever to cause the same to swing onits pivot only after said member has expanded a ore determined extent,and means operable from the support for enabling the degree of expansionof said member necessary to swing the lever, to be altered at will.

3. A thermostat switch comprising a longitudinally expansible member tobe projected into a zone ot heat, a support for the outer end of saidmember, a lever extending lengthwise of said member Jfrom the supportand pivoted onto the member adjacent the inner end ot the latter,whereby said mem` ber expands longitudinally the adjacent end of thelever will move correspondingly, said lever adjacent its pivot having asubstantially radial shoulder, a lug ixed with respect to the member tobe engaged by said shoulder as the lever moves with the member, fixedand movable contacts mounted on the support and lever respectively, andmeans operable trom the support for adjusting the setting of the luglongitudinally of the lever.

4t. A thermostat switch comprising a longitudinally expansible member tobe projected into a zone of heat, a support for the outer end of saidmember, a lever extending lengthwise oit said member from the supportand pivoted onto the member adjacent the inner end of the latter,whereby when said member expands longitudinally the adjacent end of thelever will move correspondingly, said lever adjacent its pivot having asubstantially radial shoulder, a lug fixed with respect to the member tobe engaged by said shoulder as the lever moves with the member, anon-expansible bar to which the lug is secured projecting therefrom tothe support,

and means applied to the support end of the bar for moving the samelongitudinally, and cooperating contacts on the support and the adjacentend of the lever.

5. A structure as in claim 2 in which the lever is longitudinallyexpansible and has the same coeihcient ot expansion as said member,whereby the alinement of the contacts is maintained regardless ofexpansion.

6. A thermostat switch comprising a longitudinally expansible member tobe projected into a zone ot heat, a support for the outer end of saidmember, a lever extending lengthwise of said member from the support andpivoted onto the member adjacent the inner end of the latter, wherebywhen said member expands longitudinally the adj acent end of the leverwill move correspondingly, said lever adjacent its pivot having asubstantially radial shoulder, a lug fixed with respect to the member tobe engaged by said shoulder as the lever moves with the member, anon-expansible bar to which the lug is secured projectingtherefrom tothe support, a turnable but longitudinally immovable handle mounted onthe support and threaded onto the adjacent end of the bar, and meanspreventing rotation of the bar.

7. A structure as in claim 4, with guide means for the bar to preventturning thereof mounted in said member adjacent the pivoted end of thelever.

In testimony whereof I ax my signature.

JOHN P. SCHOENBERGER.

